The present invention is a surgical device and method. More specifically, it is a device assembly and method which provides an ultrasound transducer assembly mounted on a catheter shaft in order to ultrasonically couple to a region of tissue in a body of a patient, and still more specifically to couple to a circumferential region of tissue at a location where a pulmonary vein extends from an atrium in a patient.
The terms xe2x80x9cbody space,xe2x80x9d including derivatives thereof, is herein intended to mean any cavity or lumen within the body which is defined at least in part by a tissue wall. For example, the cardiac chambers, the uterus, the regions of the gastrointestinal tract, and the arterial or venous vessels are all considered illustrative examples of body spaces within the intended meaning.
The term xe2x80x9cbody lumen,xe2x80x9d including derivatives thereof, is herein intended to mean any body space which is circumscribed along a length by a tubular tissue wall and which terminates at each of two ends in at least one opening that communicates externally of the body space. For example, the large and small intestines, the vas deferens, the trachea, and the fallopian tubes are all illustrative examples of lumens within the intended meaning. Blood vessels are also herein considered lumens, including regions of the vascular tree between their branch points. More particularly, the pulmonary veins are lumens within the intended meaning, including the region of the pulmonary veins between the branched portions of their ostia along a left ventricle wall, although the wall tissue defining the ostia typically presents uniquely tapered lumenal shapes.
Many local energy delivery devices and methods have been developed for treating the various abnormal tissue conditions in the body, and particularly for treating abnormal tissue along the body space walls which define the various body spaces in the body. For example, various devices have been disclosed with the primary purpose of treating or recanalizing atherosclerotic vessels with localized energy delivery. Several disclosed devices and methods combine energy delivery assemblies in combination with cardiovascular stent devices in order to locally deliver energy to tissue in order to maintain patency in diseased lumens such as blood vessels. Endometriosis, another abnormal wall tissue condition which is associated with the endometrial cavity of the female and is characterized by dangerously proliferative uterine wall tissue along the surface of the endometrial cavity, has also been treated by local energy delivery devices and methods. Several other devices and methods have also been disclosed which use catheter-based heat sources for the intended purpose of inducing thrombosis and controlling hemorrhaging within certain body lumens such as vessels.
Further, more detailed examples of local energy delivery devices and related procedures such as those of the types just described above are variously disclosed in the following references: U.S. Pat. No. 4,672,962 to Hershenson; U.S. Pat. No. 4,676,258 to InoKuchi et al.; U.S. Pat. No. 4,790,311 to Ruiz; U.S. Pat. No. 4,807,620 to Strul et al.; U.S. Pat. No. 4,998,933 to Eggers et al.; U.S. Pat. No. 5,035,694 to Kasprzyk et al.; U.S. Pat. No. 5,190,540 to Lee; U.S. Pat. No. 5,226,430 to Spears et al.; and U.S. Pat. No. 5,292,321 to Lee; U.S. Pat. No. 5,449,380 to Chin; U.S. Pat. No. 5,505,730 to Edwards; U.S. Pat. No. 5,558,672 to Edwards et al.; and U.S. Pat. No. 5,562,720 to Stem et al.; U.S. Pat. No. 4,449,528 to Auth et al.; U.S. Pat. No. 4,522,205 to Taylor et al.; and U.S. Pat. No. 4,662,368 to Hussein et al.; U.S. Pat. No. 5,078,736 to Behl; and U.S. Pat. No. 5,178,618 to Kandarpa. The disclosures of these references are herein incorporated in their entirety by reference thereto.
Other previously disclosed devices and methods electrically couple fluid to an ablation element during local energy delivery for treatment of abnormal tissues. Some such devices couple the fluid to the ablation element for the primary purpose of controlling the temperature of the element during the energy delivery. Other such devices couple the fluid more directly to the tissue-device interface either as another temperature control mechanism or in certain other known applications as an actual carrier for the localized energy delivery, itself.
More detailed examples of ablation devices which use fluid to assist in electrically coupling electrodes to tissue are disclosed in the following references: U.S. Pat. No. 5,348,554 to Inran et al.; U.S. Pat. No. 5,423,811 to Imran et al.; U.S. Pat. No. 5,505,730 to Edwards; U.S. Pat. No. 5,545,161 to Inran et al.; U.S. Pat. No. 5,558,672 to Edwards et al.; U.S. Pat. No. 5,569,241 to Edwards; U.S. Pat. No. 5,575,788 to Baker et al.; U.S. Pat. No. 5,658,278 to Imran et al.; U.S. Pat. No. 5,688,267 to Panescu et al.; U.S. Pat. No. 5,697,927 to Imran et al.; U.S. Pat. No. 5,722,403 to McGee et al.; U.S. Pat. No. 5,769,846; and PCT Patent Application Publication No. WO 97/32525 to Pomeranz et al.; and PCT Patent Application Publication No. WO 98/02201 to Pomeranz et al. To the extent not previously incorporated above, the disclosures of these references are herein incorporated in their entirety by reference thereto.
Atrial Fibrillation
Cardiac arrhythmias, and atrial fibrillation in particular, persist as common and dangerous medical ailments associated with abnormal cardiac chamber wall tissue, and has been observed especially in the aging population. In patients with cardiac arrhythmia, abnormal regions of cardiac tissue do not follow the synchronous beating cycle associated with normally conductive tissue in patients with sinus rhythm. Instead, the abnormal regions of cardiac tissue aberrantly conduct to adjacent tissue, thereby disrupting the cardiac cycle into an asynchronous cardiac rhythm. Such abnormal conduction has been previously known to occur at various regions of the heart, such as, for example, in the region of the sino-atrial (SA) node, along the conduction pathways of the atrioventricular (AV) node and the Bundle of His, or in the cardiac muscle tissue forming the walls of the ventricular and atrial cardiac chambers.
Cardiac arrhythmias, including atrial arrhythmia, may be of a multiwavelet reentrant type, characterized by multiple asynchronous loops of electrical impulses that are scattered about the atrial chamber and are often self propagating. In the alternative or in addition to the multiwavelet reentrant type, cardiac arrhythmias may also have a focal origin, such as when an isolated region of tissue in an atrium fires autonomously in a rapid, repetitive fashion. Cardiac arrhythmias, including atrial fibrillation, may be generally detected using the global technique of an electrocardiogram (EKG). More sensitive procedures of mapping the specific conduction along the cardiac chambers have also been disclosed, such as, for example, in U.S. Pat. No. 4,641,649 to Walinsky et al. and Published PCT Patent Application No. WO 96/32897 to Desai. The disclosures of these references are herein incorporated in their entirety by reference thereto.
A host of clinical conditions may result from the irregular cardiac function and resulting hemodynamic abnormalities associated with atrial fibrillation, including stroke, heart failure, and other thromboembolic events. In fact, atrial fibrillation is believed to be a significant cause of cerebral stroke, wherein the abnormal hemodynamics in the left atrium caused by the fibrillatory wall motion precipitate the formation of thrombus within the atrial chamber. A thromboembolism is ultimately dislodged into the left ventricle which thereafter pumps the embolism into the cerebral circulation where a stroke results. Accordingly, numerous procedures for treating atrial arrhythmias have been developed, including pharmacological, surgical, and catheter ablation procedures.
Several pharmacological approaches intended to remedy or otherwise treat atrial arrhythmias have been disclosed, such as for example according to the disclosures of the following references: U.S. Pat. No. 4,673,563 to Berne et al.; U.S. Pat. No. 4,569,801 to Molloy et al.; and also xe2x80x9cCurrent Management of Arrhythmiasxe2x80x9d (1991) by Hindricks, et al. However, such pharmacological solutions are not generally believed to be entirely effective in many cases, and are even believed in some cases to result in proarrhythmia and long term inefficacy. The disclosures of these references are herein incorporated in their entirety by reference thereto.
Several surgical approaches have also been developed with the intention of treating atrial fibrillation. One particular example is known as the xe2x80x9cmaze procedure,xe2x80x9d as is disclosed by Cox, J L et al. in xe2x80x9cThe surgical treatment of atrial fibrillation. I. Summaryxe2x80x9d Thoracic and Cardiovascular Surgery 101(3), pp. 402-405 (1991); and also by Cox, J L in xe2x80x9cThe surgical treatment of atrial fibrillation. IV. Surgical Techniquexe2x80x9d, Thoracic and Cardiovascular Surgery 101(4), pp. 584-592 (1991). In general, the xe2x80x9cmazexe2x80x9d procedure is designed to relieve atrial arrhythmia by restoring effective atrial systole and sinus node control through a prescribed pattern of incisions about the tissue wall. In the early clinical experiences reported, the xe2x80x9cmazexe2x80x9d procedure included surgical incisions in both the right and the left atrial chambers. However, more recent reports predict that the surgical xe2x80x9cmazexe2x80x9d procedure may be substantially efficacious when performed only in the left atrium, such as is disclosed in Sueda et al., xe2x80x9cSimple Left Atrial Procedure for Chronic Atrial Fibrillation Associated With Mitral Valve Diseasexe2x80x9d (1996). The disclosure of these cited references are herein incorporated in their entirety by reference thereto.
The xe2x80x9cmaze procedurexe2x80x9d as performed in the left atrium generally includes forming vertical incisions from the two superior pulmonary veins and terminating in the region of the mitral valve annulus, traversing the region of the inferior pulmonary veins en route. An additional horizontal line also connects the superior ends of the two vertical incisions. Thus, the atrial wall region bordered by the pulmonary vein ostia is isolated from the other atrial tissue. In this process, the mechanical sectioning of atrial tissue eliminates the arrhythmogenic conduction from the boxed region of the pulmonary veins and to the rest of the atrium by creating conduction blocks within the aberrant electrical conduction pathways. Other variations or modifications of this specific pattern just described have also been disclosed, all sharing the primary purpose of isolating known or suspected regions of arrhythmogenic origin or propagation along the atrial wall.
While the xe2x80x9cmazexe2x80x9d procedure and its variations as reported by Cox and others have met some success in treating patients with atrial arrhythmia, its highly invasive methodology is believed to be prohibitive in most cases. However, these procedures have provided a guiding principle that electrically isolating faulty cardiac tissue may successfully prevent atrial arrhythmia, and particularly atrial fibrillation caused by arrhythmogenic conduction arising from the region of the pulmonary veins.
Less invasive catheter-based approaches to treat atrial fibrillation have been disclosed which implement cardiac tissue ablation for terminating arrhythmogenic conduction in the atria. Examples of such catheter-based devices and treatment methods have generally targeted atrial segmentation with ablation catheter devices and methods adapted to form linear or curvilinear lesions in the wall tissue which defines the atrial chambers. Some specifically disclosed approaches provide specific ablation elements which are linear over a defined length intended to engage the tissue for creating the linear lesion. Other disclosed approaches provide shaped or steerable guiding sheaths, or sheaths within sheaths, for the intended purpose of directing tip ablation catheters toward the posterior left atrial wall such that sequential ablations along the predetermined path of tissue may create the desired lesion. In addition, various energy delivery modalities have been disclosed for forming atrial wall lesions, and include use of microwave, laser, ultrasound, thermal conduction, and more commonly, radiofrequency energies to create conduction blocks along the cardiac tissue wall.
Further more detailed examples of ablation device assemblies and methods for creating lesions along an atrial wall are disclosed in the following U.S. Patent references: U.S. Pat. No. 4,898,591 to Jang et al.; U.S. Pat. No. 5,104,393 to Isner et al.; U.S. Pat. No. 5,427,119; U.S. Pat. No. 5,487,385 to Avitall; U.S. Pat. No. 5,497,119 to Swartz et al.; U.S. Pat. No. 5,545,193 to Fleischman et al.; U.S. Pat. No. 5,549,661 to Kordis et al.; U.S. Pat. No. 5,575,810 to Swanson et al.; U.S. Pat. No. 5,564,440 to Swartz et al.; U.S. Pat. No. 5,592,609 to Swanson et al.; U.S. Pat. No. 5,575,766 to Swartz et al.; U.S. Pat. No. 5,582,609 to Swanson; U.S. Pat. No. 5,617,854 to Munsif; U.S. Pat. No. 5,687,723 to Avitall; U.S. Pat. No. 5,702,438 to Avitall. To the extent not previously incorporated above, the disclosures of these references are herein incorporated in their entirety by reference thereto.
Other examples of such ablation devices and methods are disclosed in the following Published PCT Patent Applications: WO 93/20767 to Stem et al.; WO 94/21165 to Kordis et al.; WO 96/10961 to Fleischman et al.; WO 96/26675 to Klein et al.; and WO 97/37607 to Schaer. To the extent not previously incorporated above, the disclosures of these references are herein incorporated in their entirety by reference thereto.
Additional examples of such ablation devices and methods are disclosed in the following published articles: xe2x80x9cPhysics and Engineering of Transcatheter Tissue Ablationxe2x80x9d, Avitall et al., Journal of American College of Cardiology, Volume 22, No. 3:921-932 (1993); and xe2x80x9cRight and Left Atrial Radiofrequency Catheter Therapy of Paroxysmal Atrial Fibrillation,xe2x80x9d Haissaguerre, et al., Journal of Cardiovascular Electrophysiology 7(12), pp. 1132-1144 (1996). The disclosures of these references are herein incorporated in their entirety by reference thereto.
In addition to those known assemblies just summarized above, additional tissue ablation device assemblies have also been recently developed for the specific purpose of ensuring firm contact and consistent positioning of a linear ablation element along a length of tissue by anchoring the element at least at one predetermined location along that length, such as in order to form a xe2x80x9cmazexe2x80x9d-type lesion pattern in the left atrium. One example of such assemblies includes an anchor at each of two ends of a linear ablation element in order to secure those ends to each of two predetermined locations along a left atrial wall, such as at two adjacent pulmonary veins, so that tissue may be ablated along the length of tissue extending therebetween.
In addition to attempting atrial wall segmentation with long linear lesions for treating atrial arrhythmia, other ablation device and method have also been disclosed which are intended to use expandable members such as balloons to ablate cardiac tissue. Some such devices have been disclosed primarily for use in ablating tissue wall regions along the cardiac chambers. Other devices and methods have been disclosed for treating abnormal conduction of the left-sided accessory pathways, and in particular associated with xe2x80x9cWolff-Parkinson-Whitexe2x80x9d syndrome various such disclosures use a balloon for ablating from within a region of an associated coronary sinus adjacent to the desired cardiac tissue to ablate. Further more detailed examples of devices and methods such as of the types just described are variously disclosed in the following published references: Fram et al., in xe2x80x9cFeasibility of RF Powered Thermal Balloon Ablation of Atrioventricular Bypass Tracts via the Coronary Sinus: In vivo Canine Studies,xe2x80x9d PACE, Vol. 18, p 1518-1530 (1995); xe2x80x9cLong-term effects of percutaneous laser balloon ablation from the canine coronary sinusxe2x80x9d, Schuger CD et al., Circulation (1992) 86:947-954; and xe2x80x9cPercutaneous laser balloon coagulation of accessory pathwaysxe2x80x9d, McMath L P et al., Diagn Ther Cardiovasc Interven 1991; 1425:165-171. The disclosures of these references are herein incorporated in their entirety by reference thereto.
Arrhythmias Originating from Foci in Pulmonary Veins
Various modes of atrial fibrillation have also been observed to be focal in nature, caused by the rapid and repetitive firing of an isolated center within cardiac muscle tissue associated with the atrium. Such foci may act as either a trigger of atrial fibrillatory paroxysmal or may even sustain the fibrillation. Various disclosures have suggested that focal atrial arrhythmia often originates from at least one tissue region along one or more of the pulmonary veins of the left atrium, and even more particularly in the superior pulmonary veins.
Less-invasive percutaneous catheter ablation techniques have been disclosed which use end-electrode catheter designs with the intention of ablating and thereby treating focal arrhythmias in the pulmonary veins. These ablation procedures are typically characterized by the incremental application of electrical energy to the tissue to form focal lesions designed to terminate the inappropriate arrhythmogenic conduction.
One example of a focal ablation method intended to treat focal arrhythmia originating from a pulmonary vein is disclosed by Haissaguerre, et al. in xe2x80x9cRight and Left Atrial Radiofrequency Catheter Therapy of Paroxysmal Atrial Fibrillationxe2x80x9d in Journal of Cardiovascular Electrophysiology 7(12), pp. 1132-1144 (1996) (previously incorporated by reference above). Haissaguerre, et al. discloses radiofrequency catheter ablation of drug-refractory paroxysmal atrial fibrillation using linear atrial lesions complemented by focal ablation targeted at arrhythmogenic foci in a screened patient population. The site of the arrhythmogenic foci were generally located just inside the superior pulmonary vein, and the focal ablations were generally performed using a standard 4 mm tip single ablation electrode.
Another focal ablation method of treating atrial arrhythmias is disclosed in Jais et al., xe2x80x9cA focal source of atrial fibrillation treated by discrete radiofrequency ablation,xe2x80x9d Circulation 95:572-576 (1997). The disclosure of this reference is herein incorporated in its entirety by reference thereto. Jais et al. discloses treating patients with paroxysmal arrhythmias originating from a focal source by ablating that source. At the site of arrhythmogenic tissue, in both right and left atria, several pulses of a discrete source of radiofrequency energy were applied in order to eliminate the fibrillatory process.
Other assemblies and methods have been disclosed addressing focal sources of arrhythmia in pulmonary veins by ablating circumferential regions of tissue either along the pulmonary vein, at the ostium of the vein along the atrial wall, or encircling the ostium and along the atrial wall. More detailed examples of device assemblies and methods for treating focal arrhythmia as just described are disclosed in Published PCT Patent Application No. WO 99/02096 to Diederich et al., and also in the following pending U.S. Patent Applications: U.S. Ser. No. 08/889,798 for xe2x80x9cCircumferential Ablation Device Assemblyxe2x80x9d to Michael D. Lesh et al., filed Jul. 8, 1997; U.S. Ser. No. 08/889,835 for xe2x80x9cDevice and Method for Forming a Circumferential Conduction Block in a Pulmonary Veinxe2x80x9d to Michael D. Lesh, filed Jul. 8, 1997; U.S. Ser. No. 09/199,736 for xe2x80x9cCircumferential Ablation Device Assemblyxe2x80x9d to Chris J. Diederich et. al., filed Feb. 3, 1998; and U.S. Ser. No. 09/260,316 for xe2x80x9cDevice and Method for Forming a Circumferential Conduction Block in a Pulmonary Veinxe2x80x9d to Michael D. Lesh.
Another specific device assembly and method which is intended to treat focal atrial fibrillation by ablating a circumferential region of tissue between two seals in order to form a conduction block to isolate an arrhythmogenic focus within a pulmonary vein is disclosed in U.S. Pat. No. 5,938,660 and a related Published PCT Patent Application No. WO 99/00064. The disclosures of these references are herein incorporated in their entirety by reference thereto
In particular, certain tissue ablation device assemblies which incorporate ultrasound energy sources to tissue have been observed to be highly efficient and effective for ablating such circumferential regions of tissue where pulmonary veins extend from atria. However, the efficiency of ultrasonic output from such a source has been observed to be directly related to the structural coupling of the transducer to the underlying delivery member or catheter shaft. The transducer is damped whenever it is in contact with any sort of mounting means between the back or inner side of the transducer and the catheter shaft, even according to known modes using elastomeric mounting structures sandwiched between the transducer and the shaft, though to a reduced extent. Several known ultrasound transducer mounting examples provide support structures that extend between the transducer and the underlying support member, such that for example the transducer rests on the support member which rests on the delivery member. Further more detailed examples of such ultrasound transducer support structures are disclosed in the following references: U.S. Pat. No. 5,606,974 to Castellano; and U.S. Pat. No. 5,620,479 to Diederich. The disclosures of these references are herein incorporated in their entirety by reference thereto. Further examples of structural support designs for ultrasound transducers on catheter shafts are disclosed in published PCT Patent Application PCT/U.S.98/09554 (WO98/49957) to Diederich et al.
Further to the previously disclosed ultrasound transducer mounting structures and arrangements, it is desirable for any such mounting structure to provide sufficient support and positioning for the transducer, and also provide for air backing between the transducer and the underlying delivery shaft in order to isolate ultrasound transmission radially away from the catheter shaft and toward tissue surrounding the shaft. In addition, it has further been observed that such airbacking helps prevent heat build-up in the region, as the vibrational ultrasound energy has been observed to superheat other materials in contact therewith which absorb the energy (airbacking actually reflects the energy radially outwardly as desired). Such needs for airbacking are believed to be particularly true for high operational powers associated with therapeutic ultrasound ablation transmission, as opposed to the much lower power diagnostic ultrasound assemblies which are often fixed to delivery members without any airbacking (not nearly enough energy to do the kind of material damage a therapeutic ablation energy source emits). In view of these desires, it is further desired to support the transducer as described although while minimizing the vibrational damping of the transducer during operation.
This invention provides various catheter constructions and associated methods of manufacture for mounting an ultrasound transducer onto a catheter shaft and while minimizing the damping of the transducer associated with the structural coupling to the shaft. In several of the construction variations, the transducer is suspended about an inner member (e.g., the catheter shaft) absent any support structure between the inner member and the transducer along the length of the transducer. That is, transducer mounting is accomplished without the use of internal mounting members and/or elastic member between the inner member and the transducer. Such mounting arrangements support the transducer and are attached to the inner member (or to an assembly of members) at points proximal and distal of the ultrasound transducer.
The embodiments of the invention are also generally adapted to capture air, or another gas as would be apparent to one of ordinary skill, within the mounting structures in order to xe2x80x9cair backxe2x80x9d the transducer. That is, these modes of suspension maintain an air gap between the transducer and the catheter shaft in order to maximize radially outward propagation of the ultrasound waves, as introduced above. In addition, the air space desirably is sealed to prevent fluid infiltration, be it blood or water.
Therefore, according to one mode of the invention, a tissue ablation system includes an ultrasound ablation element mounted on a distal end portion of a delivery member such as an elongate catheter body. A radial separation defines a radial separation area between the ultrasound ablation element and the distal end portion. Further to this mode, the ablation element is mounted onto the catheter shaft without a support structure extending across the radial separation area between the ultrasound ablation element and the catheter shaft.
In one aspect of this mode, a gas is captured within the radial separation area, and the radial separation area may also be sealed to substantially prevent an external fluid from entering the radial separation area, such as blood or another fluid.
In another aspect of this mode, the ultrasound ablation element is adapted to ablate a circumferential region of tissue at a location where a pulmonary vein extends from an atrium in a patient.
In another aspect of this mode, the ultrasound ablation element provides a cylindrical ultrasound transducer that has an inner surface that forms an inner bore. The inner surface is positioned over and around the distal end portion such that the radial separation area is located between the inner surface and the distal end portion.
In another aspect of this mode, the ultrasound ablation element uses a piezoceramic ultrasound transducer, wherein according to another aspect the ultrasound ablation element provides an array of ultrasound transmissive panels.
In another aspect of this mode, an external cover layer is disposed around the ultrasound ablation element and distal end portion such that the ultrasound ablation element is positioned between the external cover layer and the distal end portion. In one variation of this aspect, this external cover layer includes an adhesive. In another variation, the cover layer provides an external cover member that surrounds the ultrasound ablation element, and also provides an adhesive layer between the cover member and the ultrasound ablation element. In still a further variation, one end of the external cover layer is secured to the underlying catheter body distally of the ultrasound ablation element, and the other end of the external cover layer is secured to the catheter body proximally of the ultrasound ablation element.
In another aspect of this mode, the ultrasound ablation element comprises first and second end portions, first and second mounting flanges extend axially from said first and second end portions, respectively, relative to the longitudinal axis, and the first and second mounting flanges are secured to the distal end portion at first and second locations, respectively, which are outside of the radial separation area. According to one variation of this aspect, one or more end caps, which may beneficially be polymeric or elastomeric, may be provided between the flanges and the catheter shaft. In another variation, the mounting flanges provide a recess on one end which engages the ultrasound ablation element. Still further, the first and second mounting flanges may be connected, such as for example in one beneficial design where the flanges extend from an integral overall housing or shell or structure bridging across the length of the ultrasound transducer.
In another aspect of this mode, a tubular member is used to mount the transducer to the catheter body. The tubular member""s ends are secured to first and second locations, respectively, along the catheter body, and the ultrasound ablation element is secured to the exterior surface of an intermediate portion between the two ends of the tubular member.
In another aspect of this mode, an expandable member is also located along the distal end portion of the elongate catheter body. In one variation of this aspect, an outer wall of the expandable member encloses the ultrasound ablation element mounted onto the catheter shaft body. Further to this aspect, the transducer is adapted to ultrasonically couple to tissue engaged by the expandable member""s outer wall when expanded. In further more detailed variation, the expandable member and ablation element are specifically s adapted to engage and ablate a circumferential region of tissue at a location where a pulmonary vein extends from an atrium in a patient.
In still a further aspect of this mode, a mounting assembly is coupled to the ultrasound ablation element and also to the distal end portion at at least one other location which is outside of the radial separation area. The mounting assembly according to this aspect mounts the ultrasound ablation element onto the distal end portion without extending radially across the radial separation area between the distal end portion and the ultrasound ablation element.
Another mode of the invention provides a particular ultrasound transducer assembly for use with a delivery member in a tissue ablation system. The assembly includes a cylindrical ultrasound transducer coupled to a mounting assembly with a first mounting flange extending from one end of the transducer and a second mounting flange extending from a second end of the transducer. The first and second mounting flanges are adapted to be secured to the delivery member in order to mount the cylindrical ultrasound transducer to the delivery member to form at least in part a tissue ablation device assembly.
In one aspect of this mode, the first and second mounting flanges are connected. According to one particular variation of this aspect, the mounting assembly provides a mounting member with an intermediate portion coupled to the cylindrical ultrasound transducer, and two opposite end portions extending beyond the transducer""s ends for mounting onto a catheter shaft. In still a further variation, the intermediate portion of the mounting member surrounds the outside of the cylindrical ultrasound transducer. The transducer may be secured to and suspended inwardly from an inner surface of that intermediate portion such that by securing the mounting member""s ends to the underlying catheter shaft the transducer is held over and around the shaft. In yet another variation, it is the cylindrical transducer that surrounds the intermediate portion of the mounting member. According to another mounting member variation, the cylindrical ultrasound transducer is housed within a cylindrical space formed between outer and inner layers along the intermediate portion of the mounting member.
According to another aspect of this mode, the mounting flanges are tubular members which have a reduced diameter section at one end with a smaller inner diameter than the outer diameter of the cylindrical ultrasound transducer. The reduced diameter section is adapted to be secured around the delivery member.
Another mode of the invention provides a method for manufacturing a tissue ablation device assembly. According to this method, first and second mounting flanges are mounted to first and second ends, respectively, of a cylindrical ultrasound transducer. The flanges are also mounted to first and second locations, respectively, along a distal end portion of a delivery member such that the cylindrical ultrasound transducer is between and does not extend over the first and second locations.
According to various aspects of this method mode, one or both of the mounting flanges may be mounted to the transducer either before or after mounting to the delivery member. In another aspect, the mounting flanges are connected by an intermediate member which is mounted to the cylindrical ultrasound transducer.
Another mode of the invention provides a method for manufacturing an ultrasound transducer assembly for use with a delivery member in a tissue ablation system. According to this method mode, first and second mounting flanges are mounted to opposite ends of a cylindrical ultrasound transducer such that the flanges extend from the transducer""s ends in order to be secured to the delivery member to thereby mount the cylindrical ultrasound transducer to the delivery member and form, at least in part, a tissue ablation device assembly.
According to one further aspect of this mode, the first and second mounting flanges are connected along the cylindrical ultrasound transducer.
According to various additional aspects, the mounting flanges may be mounted to the ultrasound transducer either at the same time or in series, and the mounting flanges may also be connected, such as by being different parts of one common member.
In another aspect of this mode, the cylindrical ultrasound transducer is located within a housing from which the mounting flanges extend, wherein the mounting flanges may be separate members attached to the housing or may be formed integrally with at least a portion of the housing.
In still a further aspect of the cylindrical ultrasound transducer according to this method mode, the transducer is formed from an array of ultrasound transducer panels which may be actuatable together or, in a particular embodiment, separately.
The mounting flanges of this method mode may also be tubular such that they are adapted to mount at one end to the circumference of the cylindrical ultrasound transducer and at the other end over and around an underlying catheter shaft.
According to further beneficial embodiments, the ultrasound transducer apparatus and method modes just summarized are applied in a circumferential ablation device assembly which is adapted to couple to and ablate a circumferential region of tissue at a location where a pulmonary vein extends from an atrium. Moreover, the modes described for use with a circumferential ultrasound transducer may also be adapted for use with non-circumferential types of transducers, such as incorporating panel transducers that also benefit by being air backed without mounting members physically located and extending between such transducers and an underlying catheter shaft.